The concentration of calcium ions within nerve cells is a critical factor in controlling neural activity. Two aspects of calcium transport and disposition in the nervous system will be studied. (1) By using isolated superfused superior cervical ganglia from cats a procedure has been developed to localize accumulated 45Ca into two gross divisions within the ganglia, the pre- and post-ganglionic compartments. Thus it is possible to examine not only factors that increase or decrease total 45Ca uptake (or efflux) from the ganglion, such as electrical stimulation, the effects of neuroactive drugs (e.g. diphenylhydantoin), and ionic gradients, but it is also possible to distinguish between pre-and post-ganglionic effects of such factors. The goal is to define sites and modes of action of agents affecting calcium transport in a functioning synaptic system. (2) Membrane fractions from rat brain contain an ATPase that, in the presence of optimal concentrations of MgCl2, is stimulated by low concentrations of CaCl2. This (Ca plus Mg) minus ATPase, which is reminiscent of Ca - transport ATPases in red blood cell membranes and in the sarcoplasmic reticulum of muscle, also appears to be associated with Ca-transport. Initial studies have begun on purifying and characterizing this enzyme. Major emphasis is directed at delineating the enzymatic reaction mechanism, and relating this to the transport process. In addition, studies to define more precisely subcellular localization and factors influencing enzymatic activity are proposed.